Compound spring assembly

ABSTRACT

A compound spring assembly comprising an upper assembly of connected coils supported by a grid at the upper side of a rigid frame, and a buttressing assembly of connected coils supported within the frame at the underside of the grid in compression by a member stretched taut across the underside of the frame and secured thereto.

Unite States atet Earle 51 Aug. 15, 1972 COOUNI) SPRING ASSE I51 LY [72] Inventor: Clarence W. Earle, North Oxford,

Mass.

[73] Assignee: Webster Spring (10., Inc., Oxford,

Mass.

[22] Filed: July 8, 1970 [21] Appl. No.: 53,182

[52] US. Cl ..267/92 [51] Int. Cl. ..F16c 3/04 [58] Field of Search ..267/88, 91, 92

[56] References Cited UNITED STATES PATENTS 1,563,692 12/1925 Denham ..267/92 871,871 11/1907 Hirschman ..267/92 2,854,066 9/1958 Sternberg ..267/92 3,231,906 2/1966 Keeble ..267/91 X FOREIGN PATENTS OR APPLICATIONS 243,825 12/1925 Great Britain ..267/92 323,386 l/l930 Great Britain ..267/92 Primary Examiner-James B. Marbert Att0rneyRoberts, Cushman & Grover 5 7 ABSTRACT A compound spring assembly comprising an upper assembly of connected coils supported by a grid at the upper side of a rigid frame, and a buttressing assembly of connected coils supported within the frame at the underside of the grid in compression by a member stretched taut across the underside of the frame and secured thereto.

5 Claims, 2 Drawing Figures COMPOUND SPRING ASSEMBLY BACKGROUND OF THE INVENTION A coil spring assembly for furniture seats and the like is shown in US. Pat. No. 2,9l0,l 14 comprising an assembly of coil springs supported at their lower ends by a rigid grid, with the coils extending upwardly from the grid and providing, in conjunction with a border wire secured to their upper ends, a supporting surface suitable for a cushion. The aforesaid structure is especially designed to be prefabricated and installed as a unit into a chair frame or the like to eliminate the prior practice of hand tying of the springs and to insure uniformity and stability throughout the spring structure. The purpose of the present invention is to improve on the aforesaid structure to provide for a deeper cushioning effect while maintaining the stability desired without loss of the advantages of the aforesaid structure, to wit, a prefabricated structure which may be installed as a unit.

SUMMARY In accordance with the foregoing, the invention comprises a rigid grid, a cushion-receiving spring platform secured to one side of the grid and a buttressing spring platform secured to the other side, said grid being adapted to be supported within a frame at the upper side with a cushion-receiving spring platform extending upwardly therefrom and the buttressing platform extending downwardly therefrom into the frame into compressive engagement with means secured to the lower side of the frame yieldably to hold the cushionreceiving spring platform at said upper side. There are connecting elements adapted to secure the opposite ends of the grid to the frame at the upper side, the connecting elements at one end being rigid and those at the other end yielding, the yielding connecting elements holding the grid depressed against the buttressing platform. The coil springs constituting the platforms are arranged with their axes perpendicular to the grid with the border coils connected to the grid, the intermediate coils being connected to each other and to the border coils. A sheet of burlap is disposed between the ends of the coils of each platform and the grid. The end loops of the outer ends of the coil springs of each platform are connected to each other and a border wire is connected to the end loops of the border coils at one side.

The invention will now be described in greater detail with reference to the accompanying drawings wherein:

FIG. 1 is a fragmentary elevation of the compound spring assembly mounted in a frame comprising a component of an article of furniture; and

FIG. 2 is a plan view of the structure broken away below the top successively in the planes 2a-2a, 2b-2b and 2c2c of FIG. 1.

Referring to the drawings (FIG. 1), the compound spring assembly comprises a rigid grid 10, a cushionreceiving spring platform 12 secured to its upper side and a buttress spring platform 14 secured to its lower side, supported within a rigid frame 16 comprising a component of an article of furniture, for example, a seat frame, with the platform 12 supported above the seat frame and the platform 14 supported within the seat frame. The unit comprising the grid and the platforms 12 and 14 secured to its opposite sides is adapted to be prefabricated for mounting within the seat frame 16 by the simple expedient of dropping it into the frame and securing the ends of the grid to the upper edge of the seat frame. For this purpose, the grid, which is a rigid wire frame having spaced parallel sides 18 and ends 20, has connected to its ends 20 connecting elements 22 and 24 which are adapted to be fastened to the opposite ends of the seat frame 16. The connecting elements 22, of which there are two, comprise angle bracket members 26 connected to the upper edge of the seat frame, each of which has a loop 28 which encircles the end member 20 of the grid at that end which unyieldingly connect that end of the grid to the frame. The connecting means 24 at the opposite end, of which there are two, comprise angular bracket members 30 fastened to the upper edge of the frame and coiled springs 32 connected between the upper portions of these brackets and the end member 20 of the grid at that end.

The grid itself, in addition to the side and end wires, is crossed longitudinally and transversely by wires 34 and 36 which are secured at their opposite ends to the side and end wires of the grid and at their crossings to each other.

The spring platforms are comprised of spring coils disposed with their axes perpendicular to the grid in spaced parallel rows, with the end loops of the coils in each row overlapping and connected to each other and with the overlapping portion of the end loops in ad- 30 jacent rows connected to each other by transversely extending wires 38 which contain at intervals, corresponding to the spacing of the rows, knots 40 which lock the end loops to each other. The lower ends of the border loops at the upper side of the grid and the upper ends of the border loops of the coils at the underside of the grid are connected to the side and end wires of the grid by fastening 44 in the form of clips of wire. The coils intermediate the. border coils are unsecured, that is, the loops at the lower ends of the coils at the upper side and the loops at the upper ends of the coils at the lower side are unattached to the grid and so free to move laterally to some extent even though constrained by the connecting wires 38. A sheet of burlap 46 is placed between the lower ends of the coils at the upper side of the grid and another sheet of burlap 48 is placed between the grid and the upper ends of the coils at the lower side. Preferably the edges of these sheets of burlap are secured to the edges of the grid by the fastening means 44.

The loops at the upper ends of the coils at the upper side of the grid are enclosed within a border wire 50 having spaced parallel sides 52 and ends 54 and the loops at the upper ends of the border coils are secured to this border wire along the sides and ends by a helical connecting wire 56.

Except for the spring coils at the opposite ends of the spring platform at the upper side of the grid, all of the spring coils taper from their ends toward their midsection, the end loops at opposite ends being of corresponding diameter. The spring coils at opposite ends of the platform at the upper side, however, are coneshaped, that is, taper from their upper ends from a diameter corresponding to that of the diameters of the other coils in the platform to a much smaller diameter at their lower ends and these lower ends are secured to the grid over depressions 58 formed in the longitudinal wires 34 and locking wires 60 passed through the depressions. The spring coils in the platform at the underside of the grid are all of the same size and configuration and unlike the coils at the upper side of the grid, the loops at the lower ends of the coils at the lower side of the grid are not connected to a border wire.

The spring platform 14 at the underside of the grid buttresses the grid and the spring platform at the upper side thereof and for this purpose is held under compression by means of a member 60 stretched taut across the underside of the frame 16, comprising a sheet of burlap, the edges of which are secured by fastenings 62 to the lower edge of the frame. Desirably, stay wires 64, of which there are two, are supported in spaced parallel relation against the underside of the burlap 60 between the ends of the frame 16 by springs 66 at their opposite ends connected at one end to loops 68 at the ends of the stay 64 and at their opposite ends to straps 70 secured to the upper edge of the frame 16 so as to exert a strong upward pressure upon the burlap and thus to hold the springs in the lower platform under such compression as to in turn hold the grid slightly elevated from the upper edge of the frame 16.

As pointed out heretofore, the compound spring assembly comprising the grid and the upper and lower spring platforms can be prefabricated and so installation in a chair frame or like article of furniture can be easily accomplished by the simple expedient of connecting the ends of the grid to the upper side of the frame and then fastening the burlap and the stay wires to the underside of the frame.

While burlap is the preferred material employed between the grid and the ends of the springs and at the lower side of the frame any sheet material which is insulative, durable and sufficiently strong may be substituted therefor.

It should be understood that the present disclosure is for the purpose of illustration only and that this invention includes all modifications and equivalents falling within the scope of the appended claims.

I claim:

1. A compound spring assembly comprising a rigid grid, a cushion-receiving spring platform secured to one side of the grid and a buttressing spring platform secured to the other side, said grid being adapted to be supported within a frame at the level of the top side thereof with the cushion-receiving spring platform extending upwardly from the plane of the top side and the buttressing platform extending downwardly therefrom within the frame to the plane of the bottom side into compressive engagement with means secured across the bottom side of the frame yieldably to hold the cushion-receiving spring platform above the plane of the top side, means for non-yieldably connecting the front edge of the grid to the top side of the frame at the front, means for yieldably connecting the rear edge of the grid to the top side of the frame at the back, said non-yielding and yielding means collectively preventing movement of the grid in its plane relative to the front and rear of the frame while permitting it to yield downwardly relative to its front edge, said spring platforms comprising coiled springs above and below the grid, the adjacent ends of which have as a common sup port the grid.

2. A compound c011 sprmg assembly according to claim 1, wherein the coil springs constituting the platforms are arranged with their axes perpendicular to the grid; characterized in that only the border coils are connected to the grid, the intermediate coils being connected to each other and to the border coils, and wherein there is a sheet of burlap disposed between the ends of the coils and the grid at each side.

3. A compound coil spring assembly according to claim 2, wherein the end loops at the outer ends of the coil springs of each platform are connected to each other, and a border wire is connected to the end loops of the border coils at the one side.

4. A compound spring assembly according to claim 1, wherein there is means connecting the end loops of the coil springs engaged with the grid to each other and the end loops of the border coils to the grid, leaving the end loops of the intermediate coils unattached to the grid, means connecting the end loops of the opposite ends of the coil springs at each side to provide a structurally stable, yieldable spring platform at each side, the end loops at the outer ends of the coil springs at each side occupying a common plane, and a border wire surrounding the end loops of the outer ends of the coil springs at the top side to which the end loops of the border coils are secured, said means secured across the bottom side being compressively engaged with the outer ends of the coil springs at the bottom side.

5. A compound spring assembly according to claim 1, wherein the means secured across the lower side of the frame comprises stays extending transversely of the lower side of the frame. 

1. A compound spring assembly comprising a rigid grid, a cushion-receiving spring platform secured to one side of the grid and a buttressing spring platform secured to the other side, said grid being adapted to be supported within a frame at the level of the top side thereof with the cushion-receiving spring platform extending upwardly from the plane of the top side and the buttressing platform extending downwardly therefrom within the frame to the plane of the bottom side into compressive engagement with means secured across the bottom side of the frame yieldably to hold the cushion-receiving spring platform above the plane of the top side, means for non-yieldably connecting the front edge of the grid to the top side of the frame at the front, means for yieldably connecting the rear edge of the grid to the top side of the frame at the back, said non-yielding and yielding means collectively preventing movement of the grid in its plane relative to the front and rear of the frame while permitting it to yield downwardly relative to its front edge, said spring platforms comprising coiled springs above and below the grid, the adjacent ends of which have as a common support the grid.
 2. A compound coil spring assembly according to claim 1, wherein the coil springs constituting the platforms are arranged with their axes perpendicular to the grid; characterized in that only the border coils are connected to the grid, the intermediate coils being connected to each other and to the border coils, and wherein there is a sheet of burlap disposed between the ends of the coils and the grid at each side.
 3. A compound coil spring assembly according to claim 2, wherein the end loops at the outer ends of the coil springs of each platform are connected to each other, and a border wire is connected to the end loops of the border coils at the one side.
 4. A compound spring assembly according to claim 1, wherein there is means connecting the end loops of the coil springs engaged with the grid to each other and the end loops of the border coils to the grid, leaving the end loops of the intermediate coils unattached to the grid, means connecting the end loops of the opposite ends of the coil springs at each side to provide a structurally stable, yieldable spring platform at each side, the end loops at the outer ends of the coil springs at each side occupying a common plAne, and a border wire surrounding the end loops of the outer ends of the coil springs at the top side to which the end loops of the border coils are secured, said means secured across the bottom side being compressively engaged with the outer ends of the coil springs at the bottom side.
 5. A compound spring assembly according to claim 1, wherein the means secured across the lower side of the frame comprises stays extending transversely of the lower side of the frame. 